Science at ALCF

A snapshot of turbulent magnetic field lines (red) inside a coronal hole that expands from a small patch on the solar surface to 5 solar radii. Alfven waves (AW), launched by convective motions on the photosphere, propagate in the inhomogeneous Solar atmosphere producing primary reflected waves that interact non-linearly with the outward waves, driving a turbulent cascade. This cascade continues with secondary reflections in a very complex interplay between wave reflections and nonlinear interactions. Selected slices across the simulation domain show contours of plasma current, indicating the generation of small scale structures where the turbulent energy ultimately dissipates, heating the ambient plasma.Jean Perez, University of New Hampshire

Petascale Simulations of Inhomogeneous Alfvén Turbulence in the Solar Wind

PI Name:

Jean C. Perez

PI Email:

jeanc.perez@unh.edu

Institution:

University of New Hampshire

Allocation Program:

INCITE

Allocation Hours at ALCF:

100 Million

Year:

2014

Research Domain:

Physics

Evidence from spacecraft observations suggest that Alfvén wave (AW) turbulence, described by the model of incompressible magnetohydrodynamic (MHD), is important for heating the solar wind at large distances from the sun, though the precise role it plays in the origin of the solar wind is less clear. Reasons for this uncertainty include the lack of in situ measurements of solar wind closer to the sun, in the region where most of the heating and acceleration occur, and the difficulty in modeling this problem theoretically.

This project’s primary objective is to carry out large numerical simulations designed to advance our understanding of reduced MHD turbulence in an inhomogeneous background, which includes the physics of wave reflections that is present near the sun. Because such reflections significantly increase the complexity of the turbulence dynamics, reflection-driven AW turbulence had remained beyond the realm of modern supercomputers. As such, researchers will investigate the fundamental properties of reflection-driven Alfvén wave turbulence and simulate it in realistic coronal conditions to assess its contribution toward coronal heating and the origin of the solar wind.

Researchers will also use the simulations to produce virtual in situ spacecraft measurements, similar to measurements obtained by spacecraft probing the solar wind. Understanding solar wind measurements will prove crucial for interpreting data derived from the upcoming Solar Probe Plus mission, which is scheduled to perform several fly-bys near the critical Alfvén point, precisely the region covered by the numerical simulations.